Conventionally, when an event is being recorded by a plurality of cameras, video signals from the cameras are supplied to a video-mixer, where an operator can watch the various video signals and decide when and how to carry out a switchover from one of the cameras to another. In this way, the video-mixer provides an output signal which, during a first time interval, is derived from a first video camera and during a second time interval, from a second camera.
It is popular to carry out the switchover as a so called “wipe”. During the wipe, a border moves through the image of the output video signal, an image portion from the first input video signal being displayed on one side of the border and an image portion from the second input signal on the other. At the end of the wipe, only the second input video signal is output from the mixer. The impression on a viewer is similar to that of a wiper moving across the windscreen of a car.
Such a wipe may be ugly to look at if the composition of the images in the two video signals is inappropriate. Therefore, a wipe cannot be carried out spontaneously, if a switchover from one input signal to another is desired. Rather, conventionally, a producer watches the video signals from the cameras simultaneously and decides when and how to carry out a wipe, and instructs accordingly the persons who operate the video-mixer and the cameras. This requires numerous staff, so that the recording is expensive. Further, since the camerapersons have to be informed of an imminent wipe in order to adapt their views accordingly, it is difficult to carry out a wipe at short notice.
Another problem is that in a live production environment the result of a wipe is irreversible: if it turns out to be ugly, there is no possibility of “rewinding” and trying again.